This invention relates generally to manufacture of semiconductor devices and more particularly to mechanical systems that position testers relative to a material handling unit in an automatic test system.
In the manufacture of semiconductor devices, the semiconductor devices are usually tested at least once during the manufacturing operation. Further processing is done on the devices based on the results of the tests. The testing might be used to separate properly operating devices from devices that fail to operate properly. However, testing can also be used to feed back data to other stages in the manufacturing operation to make adjustments that increase the yield of properly operating devices. In other instances, the test results are used to sort devices into performance categories. For example, a device might operate at data rates of 200 MHz, but not operate at data rates of 400 MHz. Following testing, the device might be classified as a 200 MHz device and sold at a lower price than a 400 MHz device.
A testing stage might also be used to make physical changes to the device under test. Many semiconductor devices with memories contain redundant elements. If defective memory cells are discovered during testing, the semiconductor device might be sent to a repair station, such as a laser repair station, where connections on the device are rearranged to disconnect the faulty cells and connect redundant elements in their places.
Testing is generally performed by Automatic Test Equipment (ATE). A tester contains the circuitry that generates and measures the electrical signals needed to determine if the device is properly functioning. A separate material handling device moves the semiconductor devices to the tester. A material handling device is often called a xe2x80x9chandlerxe2x80x9d when the semiconductor devices are being tested after they have been packaged. A material handling device might alternatively be called a xe2x80x9cproberxe2x80x9d, which is used when the semiconductor devices are tested while still on a wafer. In general, the tester and the material handling device are assembled into a work cell, with the specific characteristics of the tester and material handling device being selected based on the type of devices that are to be tested.
In manufacturing semiconductors, it is desirable that the equipment in the fabrication facility be in service as much as possible. Taking equipment out of service, even to make routine adjustments to the equipment, can reduce the cost effectiveness of the entire manufacturing operation.
For example, most testers are designed to test many different types of semiconductor devices. Because different semiconductor devices have different sizes and numbers of test points, ATE usually includes an interface unit, such as a xe2x80x9cdevice interface unitxe2x80x9d (DIB), that is configured for the specific type of device to be tested. To configure the ATE for a specific type of device, a different interface unit is installed in the ATE.
Usually, the interface unit is located between the tester and the material handling unit. To change the interface unit, it is necessary to separate the tester and material handling unit. Therefore, ATE has generally included a xe2x80x9cmanipulatorxe2x80x9d or xe2x80x9cpositionerxe2x80x9d for the tester. An example of a manipulator is shown in U.S. Pat. No. 5,931,048 entitled xe2x80x9cManipulator for Automatic Test Equipment Test Head.xe2x80x9d The manipulator in that patent is described in conjunction with a test system in which the tester has two separate piecesxe2x80x94a body and a test head. Regardless of whether the tester is in two pieces or contained within a single unit, some portion of the tester is generally positioned against the material handling unit so that the devices to be tested can be presented to the tester electronics.
Many different types of material handling devices are known. Different ones present the devices to be tested in different orientations. For example, some present the devices in a vertical plane. Others present them in a horizontal plane. For that reason, manipulators have generally been built to allow the tester to be moved with multiple degrees of freedom. In that way, regardless of the orientation in which the material handling unit presents the devices to be tested, the tester can be positioned adjacent the interface area where the material handler presents the devices. The above mentioned U.S. Pat. No. 5,931,048 is an example of a manipulator with multiple degrees of freedom.
However, providing multiple degrees of freedom makes it difficult to align the tester and the handler for proper engagement of the tester and the material handling unit. The process of attaching the tester to the material handling unit is sometimes called xe2x80x9cdocking.xe2x80x9d To aid in the docking, positioning units on the tester and the handling unit have been used. An example of positioning units are shown in U.S. Pat. No. 5,982,182 entitled xe2x80x9cInterface Apparatus for Automatic Test Equipment with Positioning Modules,xe2x80x9d which is hereby incorporated by reference.
The positioning modules of U.S. Pat. No. 5,982,182 are designed to engage when the tester is positioned near the handling device. The engagement provides a course alignment of the tester and the material handling unit. As the tester and material handler are pushed together, the shape of the positioning module accurately positions the components relative to each other. In the preferred embodiments of that patent, the positioning module included a linear actuator that could, once engaged, could draw the tester and material handling unit together.
For the relative position of the tester and the material handling unit to be accurately defined by the shape of the positioning unit, it is necessary that the manipulator not put excessive force on the tester. Therefore, preferred manipulators included a compliant mode that allowed sufficient motion of the test head. However, the motion must not be so great that the tester moves uncontrollably. The manipulator described in the above mentioned U.S. Pat. No. 5,982,182 was designed for such compliance. Another example of a manipulator with compliance is found in U.S. Pat. No. 5,949,002.
With the foregoing background in mind, it is an object of the invention to provide a manipulator for a tester that can move with limited degrees of freedom to provide course alignment, but can move with more degrees of freedom to provide compliant motion for docking.
Such a tester is provided with a manipulator that has a base member and a stage carrying the tester. The base and stage can move relative to each other, but a guide assembly constrains the degrees of freedom of that motion in areas outside a complaint zone.